Kan there is a Pos office right in front of KL Sentral?

actually not only 1 but 2 post office there.

the one i show u is i think should do parcel one: https://www.google.com/maps/place/Pos+Malay...48b707bb8e03fbf

both post office also in the same direction, after you go out from kl sentral, turn to right and walk.

the first post office you need to cross the road. it's a small building.

the 2nd post office is very big, but no need to cross road if you walk out from kl sentral and turn right as well.

here's the simple one, remember nu sentral shopping mall got a bridge that connect to monoral?

there's 2 escalators in the bridge right?

take the escalator that nearer to the kl sentral.

after go down walk straight ... that is the direction of post office.

two ways.

i) when u reach kl sentral, ask where to take genting bus.
it should be one level below kl sentral.
when you reach the place where you wait for genting bus, ask where is ascott hotel/menara shell, when you reach the main road (4 lane road), dont cross the road, just turn left, walk for about 100m, you will see it.

ii) when u reach kl sentral, ask where is aloft hotel.
when reach inside aloft, take the lift to lg3.
when you reach lg3, just walk towards the main road.
when you reach the main road, pos laju is on your right.